21 Genomes and Their Evolution - PowerPoint Presentation

Slide1

21

Genomes and Their Evolution

Lecture Presentation by Nicole Tunbridge andKathleen Fitzpatrick

Slide2

Reading the Leaves from the Tree of LifeComplete genome sequences exist for a human, chimpanzee, E. coli, brewer’s yeast, corn, fruit fly, house mouse, rhesus macaque, and many other organismsComparisons of genomes among organisms provide insights into evolution and other biological processes

Slide3

Genomics is the study of whole sets of genes and their interactionsBioinformatics is the application of computational methods to the storage and analysis of biological data

Slide4

Figure 21.1

Slide5

Figure 21.1a

House mouse (Mus musculus)

Slide6

Concept 21.1: The Human Genome Project fostered development of faster, less expensive sequencing techniquesOfficially begun as the Human Genome Project in 1990, the sequencing of the human genome was largely completed by 2003The genome was completed using sequencing machines and the dideoxy chain termination methodA major thrust of the project was development of technology for faster sequencing

Slide7

Two approaches complemented each other in obtaining the complete sequenceThe initial approach built on an earlier storehouse of human genetic informationThen J. Craig Venter set up a company to sequence the entire genome using an alternative whole-genome shotgun approach This used cloning and sequencing of fragments of randomly cut DNA followed by assembly into a single continuous sequence

Slide8

Figure 21.2-1

Cut the DNA intooverlapping fragmentsshort enough forsequencing.

1

2

Clone the fragments

in plasmid or other

vectors.

Slide9

Figure 21.2-2

Cut the DNA intooverlapping fragmentsshort enough forsequencing.

1

2

3

Clone the fragments

in plasmid or other

vectors.

Sequence each

fragment.

CGCCATCAGT

AGTCCGCTATACGA

ACGATACTGGT

Slide10

Figure 21.2-3

Cut the DNA intooverlapping fragmentsshort enough forsequencing.

1

2

3

Clone the fragments

in plasmid or other

vectors.

Sequence each

fragment.

CGCCATCAGT

CGCCATCAGT

AGTCCGCTATACGA

ACGATACTGGT

ACGATACTGGT

AGTCCGCTATACGA

⋯

CGCCATCAGTCCGCTATACGATACTGGT

⋯

4

Order the sequences

into one overall

sequence with

computer software.

Slide11

Today the whole-genome shotgun approach is widely used, though newer techniques are contributing to the faster pace and lowered cost of genome sequencingThese newer techniques do not require a cloning step These techniques have also facilitated a metagenomics approach in which DNA from a group of species in an environmental sample is sequenced

Slide12

Concept 21.2: Scientists use bioinformatics to analyze genomes and their functionsThe Human Genome Project established databases and refined analytical software to make data available on the InternetThis has accelerated progress in DNA sequence analysis

Slide13

Centralized Resources for Analyzing Genome SequencesBioinformatics resources are provided by a number of sourcesNational Library of Medicine and the National Institutes of Health (NIH) created the National Center for Biotechnology Information (NCBI)European Molecular Biology LaboratoryDNA Data Bank of JapanBGI in Shenzhen, China

Slide14

Genbank, the NCBI database of sequences, doubles its data approximately every 18 monthsSoftware is available that allows online visitors to search Genbank for matches toA specific DNA sequenceA predicted protein sequenceCommon stretches of amino acids in a proteinThe NCBI website also provides 3-D views of all protein structures that have been determined

Slide15

Figure 21.3

WD40 - Sequence Alignment Viewer

WD40 - Cn3D 4.1

CDD Descriptive Items

Name: WD40

WD40 domain, found in a number

of eukaryotic proteins that cover

a wide variety of functions

including adaptor/regulatory

modules in signal transduction,

pre-mRNA processing and

cytoskeleton assembly; typically

contains a GH dipeptide 11-24

residues from its N-terminus and

the WD dipeptide at its

C-terminus and is 40 residues

long, hence the name WD40;

Slide16

Identifying Protein-Coding Genes and Understanding Their FunctionsUsing available DNA sequences, geneticists can study genes directly The identification of protein coding genes within DNA sequences in a database is called gene annotation

Slide17

Gene annotation is largely an automated processComparison of sequences of previously unknown genes with those of known genes in other species may help provide clues about their function

Slide18

Understanding Genes and Gene Expression at the Systems LevelProteomics is the systematic study of full protein sets encoded by a genomeProteins, not genes, carry out most of the activities of the cell

Slide19

How Systems Are Studied: An ExampleA systems biology approach can be applied to define gene circuits and protein interaction networksResearchers working on the yeast Saccharomyces cerevisiae used sophisticated techniques to disable pairs of genes one pair at a time, creating double mutantsComputer software then mapped genes to produce a network-like “functional map” of their interactionsThe systems biology approach is possible because of advances in bioinformatics

Slide20

Figure 21.4

Translation andribosomalfunctions

Mitochondrialfunctions

Peroxisomal

functions

Metabolism

and

amino acid

biosynthesis

Secretion

and vesicle

transport

Protein folding and

glycosylation;

cell wall biosynthesis

Cell polarity and

morphogenesis

DNA replication

and repair

Mitosis

Nuclear

migration

and protein

degradation

Nuclear-

cytoplasmic

transport

Transcription and

chromatin-related

functions

RNA processing

Glutamate

biosynthesis

Vesicle

fusion

Amino acid

permease

pathway

Serine-

related

biosynthesis

Slide21

Figure 21.4a

Translation andribosomalfunctions

Mitochondrialfunctions

Peroxisomal

functions

Metabolism

and

amino acid

biosynthesis

Secretion

and vesicle

transport

Protein folding and

glycosylation;

cell wall biosynthesis

Cell polarity and

morphogenesis

DNA replication

and repair

Mitosis

Nuclear

migration

and protein

degradation

Nuclear-

cytoplasmic

transport

Transcription and

chromatin-related

functions

RNA processing

Slide22

Figure 21.4b

Glutamate biosynthesis

Vesiclefusion

Amino acid

permease

pathway

Serine-

related

biosynthesis

Metabolism

and

amino acid

biosynthesis

Slide23

Application of Systems Biology to MedicineThe Cancer Genome Atlas project, started in 2010, looked for all the common mutations in three types of cancer by comparing gene sequences and expression in cancer versus normal cellsThis was so fruitful, it has been extended to ten other common cancersSilicon and glass “chips” have been produced that hold a microarray of most known human genesThese are used to study gene expression patterns in patients suffering from various cancers or other diseases

Slide24

Figure 21.5

Slide25

Concept 21.3: Genomes vary in size, number of genes, and gene densityBy early 2013, over 4,300 genomes were completely sequenced, including 4,000 bacteria, 186 archaea, and 183 eukaryotesSequencing of over 9,600 genomes and over 370 metagenomes is currently in progress

Slide26

Genome SizeGenomes of most bacteria and archaea range from 1 to 6 million base pairs (Mb); genomes of eukaryotes are usually largerMost plants and animals have genomes greater than 100 Mb; humans have 3,000 MbWithin each domain there is no systematic relationship between genome size and phenotype

Slide27

Table 21.1

Slide28

Number of GenesFree-living bacteria and archaea have 1,500 to 7,500 genesUnicellular fungi have from about 5,000 genes and multicellular eukaryotes up to at least 40,000 genes

Slide29

Number of genes is not correlated to genome sizeFor example, it is estimated that the nematode C. elegans has 100 Mb and 20,100 genes, while Drosophila has 165 Mb and 14,000 genesResearchers predicted the human genome would contain about 50,000 to 100,000 genes; however the number is around 21,000Vertebrate genomes can produce more than one polypeptide per gene because of alternative splicing of RNA transcripts

Slide30

Gene Density and Noncoding DNAHumans and other mammals have the lowest gene density, or number of genes, in a given length of DNAMulticellular eukaryotes have many introns within genes and a large amount of noncoding DNA between genes

Slide31

Concept 21.4: Multicellular eukaryotes have much noncoding DNA and many multigene familiesSequencing of the human genome reveals that 98.5% does not code for proteins, rRNAs, or tRNAsAbout a quarter of the human genome codes for introns and gene-related regulatory sequences

Slide32

Intergenic DNA is noncoding DNA found between genesPseudogenes are former genes that have accumulated mutations and are nonfunctionalRepetitive DNA is present in multiple copies in the genomeAbout three-fourths of repetitive DNA is made up of transposable elements and sequences related to them

Slide33

Figure 21.6

Exons (1.5%)

Regulatory

sequences (5%)

Introns

(

∼

20%)

Unique

noncoding

DNA (15%)

Repetitive

DNA that

includes

transposable

elements

and related

sequences

(44%)

Repetitive

DNA

unrelated to

transposable

elements (14%)

L1

sequences

(17%)

Alu

elements

(10%)

Simple sequence

DNA (3%)

Large-segment

duplications (5–6%)

Slide34

Much evidence indicates that noncoding DNA (previously called “junk DNA”) plays important roles in the cellFor example, genomes of humans, rats, and mice show high sequence conservation for about 500 noncoding regions

Slide35

Transposable Elements and Related SequencesThe first evidence for mobile DNA segments came from geneticist Barbara McClintock’s breeding experiments with Indian cornMcClintock identified changes in the color of corn kernels that made sense only if some genetic elements move from other genome locations into the genes for kernel colorThese transposable elements move from one site to another in a cell’s DNA; they are present in both prokaryotes and eukaryotes

Slide36

Figure 21.7

Slide37

Figure 21.7a

Slide38

Figure 21.7b

Slide39

Movement of Transposons and RetrotransposonsEukaryotic transposable elements are of two typesTransposons, which move by means of a DNA intermediate and require a transposase enzymeRetrotransposons, which move by means of an RNA intermediate, using a reverse transcriptase

Slide40

Figure 21.8

Transposon

New copy oftransposon

DNA of

genome

Transposon

is copied

Insertion

Mobile copy of transposon

Slide41

Figure 21.9

Retrotransposon

New copy ofretrotransposon

Insertion

Mobile copy of

retrotransposon

Synthesis of a

single-stranded

RNA intermediate

RNA

Reverse

transcriptase

DNA

strand

Slide42

Sequences Related to Transposable ElementsMultiple copies of transposable elements and related sequences are scattered throughout eukaryotic genomesIn primates, a large portion of transposable element–related DNA consists of a family of similar sequences called Alu elementsMany Alu elements are transcribed into RNA molecules; some are thought to help regulate gene expression

Slide43

The human genome also contains many sequences of a type of retrotransposon called LINE-1 (L1)L1 sequences have a low rate of transposition and may have effects on gene expressionL1 transposons may play roles in the diversity of neuronal cell types

Slide44

Other Repetitive DNA, Including Simple Sequence DNAAbout 15% of the human genome consists of duplication of long sequences of DNA from one location to anotherIn contrast, simple sequence DNA contains many copies of tandemly repeated short sequences

Slide45

A series of repeating units of 2 to 5 nucleotides is called a short tandem repeat (STR)The repeat number for STRs can vary among sites (within a genome) or individuals Simple sequence DNA is common in centromeres and telomeres, where it probably plays structural roles in the chromosome

Slide46

Genes and Multigene FamiliesMany eukaryotic genes are present in one copy per haploid set of chromosomesThe rest of the genes occur in multigene families, collections of identical or very similar genesSome multigene families consist of identical DNA sequences, usually clustered tandemly, such as those that code for rRNA products

Slide47

Figure 21.10a

DNA

DNA

Direction of transcription

RNA transcripts

Nontranscribed

spacer

Transcription unit

rRNA

18S

5.8S

28S

28S

5.8S

18S

(a) Part of the ribosomal RNA gene family

Slide48

The classic examples of multigene families of nonidentical genes are two related families of genes that encode globins -globins and -globins are polypeptides of hemoglobin and are coded by genes on different human chromosomes and are expressed at different times in development

Slide49

Figure 21.10b

α

-Globin

α

2

α

-Globin

β

-Globin

β

-Globin

α

-Globin gene family

β

-Globin gene family

(b) The human α

-globin and

β

-globin gene

families

Chromosome 16

Chromosome 11

Embryo

Embryo

Adult

Fetus

and adult

Fetus

α

1

ζ



ζ



β



α

2



α

1



θ

ϵ



β

G



A



Heme

Slide50

Concept 21.5: Duplication, rearrangement, and mutation of DNA contribute to genome evolutionThe basis of change at the genomic level is mutation, which underlies much of genome evolutionThe earliest forms of life likely had only those genes necessary for survival and reproductionThe size of genomes has increased over evolutionary time, with the extra genetic material providing raw material for gene diversification

Slide51

Duplication of Entire Chromosome SetsAccidents in meiosis can lead to one or more extra sets of chromosomes, a condition known as polyploidyThe genes in one or more of the extra sets can diverge by accumulating mutations; these variations may persist if the organism carrying them survives and reproducesIn this way genes with novel functions can evolve

Slide52

Alterations of Chromosome StructureHumans have 23 pairs of chromosomes, while chimpanzees have 24 pairsFollowing the divergence of humans and chimpanzees from a common ancestor, two ancestral chromosomes fused in the human lineDuplications and inversions result from mistakes during meiotic recombinationComparative analysis between chromosomes of humans and seven mammalian species paints a hypothetical chromosomal evolutionary history

Slide53

Figure 21.11

Telomeresequences

Centromere

sequences

Telomere-like

sequences

Centromere-like

sequences

Human

chromosome

Chimpanzee

chromosomes

12

13

2

Slide54

Figure 21.12

Human chromosome

Mouse chromosomes

16

16

7

8

17

Slide55

The rate of duplications and inversions seems to have accelerated about 100 million years agoThis coincides with when large dinosaurs went extinct and mammals diversifiedChromosomal rearrangements are thought to contribute to the generation of new species

Slide56

Duplication and Divergence of Gene-Sized Regions of DNAUnequal crossing over during prophase I of meiosis can result in one chromosome with a deletion and another with a duplication of a particular regionTransposable elements can provide sites for crossover between nonsister chromatids

Slide57

Figure 21.13

Nonsisterchromatids

Gene

Transposable

element

Crossover

point

and

Incorrect pairing

of two homologs

during meiosis

Slide58

Evolution of Genes with Related Functions: The Human Globin GenesThe genes encoding the various globin proteins evolved from one common ancestral globin gene, which duplicated and diverged about 450–500 million years agoAfter the duplication events, differences between the genes in the globin family arose from the accumulation of mutations

Slide59

Figure 21.14

Ancestral globin gene

α2

α

1

ζ



ζ



β



α

2



α

1

y

θ

ϵ



β

G



A



ϵ

β

β

β

ζ

α

α

α

Duplication of

ancestral gene

Mutation in

both copies

Transposition to

different chromosomes

Further duplications

and mutations

Evolutionary time

α

-Globin gene family

on chromosome 16

β

-Globin gene family

on chromosome 11



Slide60

Subsequent duplications of these genes and random mutations gave rise to the present globin genes, which code for oxygen-binding proteinsThe similarity in the amino acid sequences of the various globin proteins supports this model of gene duplication and mutation

Slide61

Evolution of Genes with Novel FunctionsThe copies of some duplicated genes have diverged so much in evolution that the functions of their encoded proteins are now very differentFor example the lysozyme gene was duplicated and evolved into the gene that encodes -lactalbumin in mammalsLysozyme is an enzyme that helps protect animals against bacterial infection-lactalbumin is a nonenzymatic protein that plays a role in milk production in mammals

Slide62

Figure 21.15

(a) Lysozyme

(b) α–lactalbumin

(c) Amino acid sequence alignments of lysozyme and

α

–

lactalbumin

Lysozyme

α

–

lactalbumin

Lysozyme

α

–

lactalbumin

Lysozyme

α

–

lactalbumin

1

1

51

51

101

101

Slide63

Rearrangements of Parts of Genes: Exon Duplication and Exon ShufflingThe duplication or repositioning of exons has contributed to genome evolutionErrors in meiosis can result in an exon being duplicated on one chromosome and deleted from the homologous chromosomeIn exon shuffling, errors in meiotic recombination lead to some mixing and matching of exons, either within a gene or between two nonallelic genes

Slide64

Figure 21.16

EGF

EGF

EGF

EGF

EGF

F

F

F

F

F

K

K

K

Epidermal growth

factor gene with multiple

EGF exons

Fibronectin

gene with multiple

“finger” exons

Plasminogen gene with a

“

kringle

” exon

Portions of ancestral genes

TPA gene as it exists today

Exon

shuffling

Exon

duplication

Exon

shuffling

Slide65

How Transposable Elements Contribute to Genome EvolutionMultiple copies of similar transposable elements may facilitate recombination, or crossing over, between different chromosomesInsertion of transposable elements within a protein-coding sequence may block protein productionInsertion of transposable elements within a regulatory sequence may increase or decrease protein production

Slide66

Transposable elements may carry a gene or groups of genes to a new positionTransposable elements may also create new sites for alternative splicing in an RNA transcriptIn all cases, changes are usually detrimental but may on occasion prove advantageous to an organism

Slide67

Concept 21.6: Comparing genome sequences provides clues to evolution and developmentComparisons of genome sequences from different species reveal much about the evolutionary history of lifeComparative studies of embryonic development are beginning to clarify the mechanisms that generated the diversity of life-forms present today

Slide68

Comparing GenomesGenome comparisons of closely related species help us understand recent evolutionary events Relationships among species can be represented by a tree-shaped diagram

Slide69

Figure 21.17

Bacteria

Eukarya

Archaea

Most recent

common

ancestor

of all living

things

Billions of years ago

4 3 2 1 0

Chimpanzee

Human

Mouse

Millions of years ago

70 60 50 40 30 20 10 0

Slide70

Comparing Distantly Related SpeciesHighly conserved genes have changed very little over timeThese help clarify relationships among species that diverged from each other long agoBacteria, archaea, and eukaryotes diverged from each other between 2 and 4 billion years agoHighly conserved genes can be studied in one model organism, and the results applied to other organisms

Slide71

Comparing Closely Related SpeciesGenomes of closely related species are likely to be organized similarlyFor example, using the human genome sequence as a guide, researchers were quickly able to sequence the chimpanzee genomeAnalysis of the human and chimpanzee genomes reveals some general differences that underlie the differences between the two organisms

Slide72

Human and chimpanzee genomes differ by 1.2% at single base-pairs, and by 2.7% because of insertions and deletionsSequencing of the bonobo genome in 2012 reveals that in some regions there is greater similarity between human and bonobo or chimpanzee sequences than between chimpanzee and bonobo

Slide73

A number of genes are apparently evolving faster in the human than in the chimpanzee or mouseAmong them are genes involved in defense against malaria and tuberculosis and one that regulates brain size

Slide74

Humans and chimpanzees differ in the expression of the FOXP2 gene, whose product turns on genes involved in vocalizationDifferences in the FOXP2 gene may explain why humans but not chimpanzees communicate by speechThe FOXP2 gene of Neanderthals is identical to that of humans, suggesting they may have been capable of speech

Slide75

Figure 21.18

Wild type: twonormal copies ofFOXP2

Heterozygote: onecopy of FOXP2disrupted

Homozygote: both

copies of

FOXP2

disrupted

Experiment

Experiment 1: Researchers cut thin sections of brain and stained

them with reagents that allow visualization of brain anatomy in a

UV fluorescence microscope.

Experiment 2: Researchers

separated each newborn pup

from its mother and recorded

the number of ultrasonic

whistles produced by the pup.

Experiment 2

Results

Experiment 1

Wild type

Heterozygote

Homozygote

Number of whistles

(No

whistles)

400

300

200

100

0

Wild

type

Hetero-

zygote

Homo-

zygote

Slide76

Figure 21.18a

Wild type: twonormal copies ofFOXP2

Heterozygote: onecopy of FOXP2disrupted

Homozygote: both

copies of

FOXP2

disrupted

Experiment

Results

Experiment 1

Wild type

Heterozygote

Homozygote

Experiment 1: Researchers cut thin sections of brain and stained

them with reagents that allow visualization of brain anatomy in a

UV fluorescence microscope.

Slide77

Figure 21.18aa

Wild type: twonormal copies ofFOXP2

Slide78

Figure 21.18ab

Heterozygote: onecopy of FOXP2disrupted

Slide79

Figure 21.18ac

Homozygote: bothcopies of FOXP2disrupted

Slide80

Figure 21.18b

Wild type: twonormal copies ofFOXP2

Heterozygote: onecopy of FOXP2disrupted

Homozygote: both

copies of

FOXP2

disrupted

Experiment

Results

Experiment 2

Experiment 2: Researchers separated each newborn pup from

its mother and recorded the number of ultrasonic whistles

produced by the pup.

Number of whistles

(No

whistles)

400

300

200

100

0

Wild

type

Hetero-

zygote

Homo-

zygote

Slide81

Figure 21.18ba

Slide82

Comparing Genomes Within a SpeciesAs a species, humans have only been around about 200,000 years and have low within-species genetic variationVariation within humans is due to single nucleotide polymorphisms, inversions, deletions, and duplicationsMost surprising is the large number of copy-number variantsThese variations are useful for studying human evolution and human health

Slide83

Widespread Conservation of Developmental Genes Among AnimalsEvolutionary developmental biology, or evo-devo, is the study of the evolution of developmental processes in multicellular organismsGenomic information shows that minor differences in gene sequence or regulation can result in striking differences in form

Slide84

Molecular analysis of the homeotic genes in Drosophila has shown that they all include a sequence called a homeoboxAn identical or very similar nucleotide sequence has been discovered in the homeotic genes of both vertebrates and invertebratesHomeobox genes code for a domain that allows a protein to bind to DNA and to function as a transcription regulatorHomeotic genes in animals are called Hox genes

Slide85

Figure 21.19

Adultfruit fly

Fruit fly embryo(10 hours)

Fruit fly

chromosome

Mouse

chromosomes

Mouse embryo

(12 days)

Adult mouse

Slide86

Related homeobox sequences have been found in regulatory genes of yeasts, plants, and even prokaryotesIn addition to homeotic genes, many other developmental genes are highly conserved from species to species

Slide87

Sometimes small changes in regulatory sequences of certain genes lead to major changes in body formFor example, variation in Hox gene expression controls variation in leg-bearing segments of crustaceans and insects In other cases, genes with conserved sequences play different roles in different species

Slide88

Figure 21.20

Thorax

Thorax

Genital

segments

Abdomen

Abdomen

(a) Expression of four

Hox

genes in the brine

shrimp

Artemia

(b) Expression of the grasshopper versions of

the same four

Hox

genes

Slide89

Figure 21.10

DNA

DNA

Direction of transcription

RNA transcripts

Nontranscribed

spacer

Transcription unit

rRNA

18S

5.8S

28S

28S

5.8S

18S

(a) Part of the ribosomal RNA gene family

α

-Globin

α

2

α

-Globin

β

-Globin

β

-Globin

α

-Globin gene family

β

-Globin gene family

(b) The human α

-globin and

β

-globin gene

families

Chromosome 16

Chromosome 11

Embryo

Embryo

Adult

Fetus

and adult

Fetus

α

1

ζ



ζ



β



α

2



α

1



θ

ϵ



β

G



A



Heme

Slide90

Figure 21.10c

DNA

Direction of transcription

RNA transcripts

Nontranscribed

spacer

Transcription unit

Slide91

Figure 21.UN01a

Globin

Alignment of Globin Amino Acid Sequences

1

1

31

31

61

61

91

91

121

121

MV

LS

P

AD

K

TN

V

KA

AWG

KVG

A

HAGE

Y

GAEAL

M

S

LT

KTE

R

TII

VS

MW

A

KIS

TQ

AD

T

IG

T

ET

L

α

1

ζ

α

1

ζ

α

1

ζ

α

1

ζ

α

1

ζ

E

RM

FLS

FPT

TK

TYFPHF

DL

S

H–

GSA

QV

KGH

E

RLFLS

HPQ

TKTY

FP

HFD

L

–

HP

GSAQLR

AH

GKK

V

AD

A

LT

N

A

VA

H

VD

DM

P

NA

LS

AL

SD

LHA

G

S

K

V

V

AA

VGDA

VK

SI

D

DI

G

GA

L

SK

L

SE

LHA

H

KL

RV

DP

V

NF

K

LL

SHC

LL

VTL

AAH

L

P

AE

FT

YI

LR

V

DP

V

NFK

LL

SH

C

LLV

TL

A

AR

FP

A

DF

T

P

AV

HA

SL

DK

FL

AS

VS

TV

LT

SK

YR

AEAH

A

AW

DK

FL

S

VV

S

SV

LT

EK

YR

Slide92

Figure 21.UN01b

Amino Acid Identity Table

α Family

β

Family

α

Family

β

Family

α

1

(alpha 1)

α

2

(alpha 2)

ζ

(zeta)

β

(beta)



(delta)

ϵ

(epsilon)

A



(gamma A)

G



(gamma G)

α

1

α

2

ζ

β



ϵ

A



G



-----

-----

-----

-----

-----

-----

-----

-----

100

61

61

45

45

38

44

44

40

93

39

39

41

41

41

76

73

73

73

71

72

42

42

42

42

80

80

99

Slide93

Figure 21.UN01c

Hemoglobin

α

α

β

β

Slide94

Figure 21.UN02

Slide95

Figure 21.UN03

Bacteria

Archaea

Eukarya

Genome

size

Number of

genes

Gene

density

Introns

Other

noncoding

DNA

Most are 1–6 Mb

1,500–7,500

Higher than in eukaryotes

None in

protein-coding

genes

Present in

some genes

Very

little

Most are 10–4,000 Mb, but a

few are much larger

5,000–40,000

Lower than in prokaryotes

(Within eukaryotes, lower

density is correlated with larger

genomes.)

Present in most genes of

multicellular eukaryotes, but

only in some genes of

unicellular eukaryotes

Can exist in large amounts;

generally more repetitive

noncoding DNA in

multicellular eukaryotes

Slide96

Figure 21.UN04

α2

α-Globin gene family

β

-Globin gene family

Chromosome 16

Chromosome 11

α

1

ζ



ζ



β



α

2



α

1



θ

ϵ



β

G



A



Slide97

Figure 21.UN05

Slide98

Figure 21.UN06